import java.util.ArrayList;
import java.util.List;

public class BinaryTree {
    static class TreeNode {
        public char val;
        public TreeNode left;//存储左孩子的引用
        public TreeNode right;//存储右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }

    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');

        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;

        return A;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null) return;
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    //遍历思路
    List<Character> list = new ArrayList<>();
    public List<Character> preorderTraversal(TreeNode root) {
        if(root == null) return list;
        //System.out.print(root.val+" ");
        list.add(root.val);
        preorderTraversal(root.left);
        preorderTraversal(root.right);
        return list;
    }
    //子问题
    public List<Character> preorderTraversal2(TreeNode root) {

        List<Character> list = new ArrayList<>();
        if(root == null) return list;
        list.add(root.val);

        List<Character> leftTree = preorderTraversal2(root.left);
        list.addAll(leftTree);

        List<Character> rightTree = preorderTraversal2(root.right);
        list.addAll(rightTree);

        return list;
    }

    // 中序遍历
    public void inOrder(TreeNode root) {
        if(root == null) return;
        inOrder(root.left);
        System.out.print(root.val+" ");
        inOrder(root.right);
    }
    // 后序遍历
    public void postOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+" ");
    }


    public static int nodeSize = 0;
    // 获取树中节点的个数
    public void size(TreeNode root) {
        if(root == null) {
            return ;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    public int size2(TreeNode root) {
        if(root == null) {
            return 0;
        }
        return size2(root.left) +
                size2(root.right)+1;
    }

    /**
     * 获取叶子节点的个数
     *  什么是叶子
     * @param root
     * @return
     */
    public static int leafSize;
    public void getLeafNodeCount(TreeNode root) {
        if(root == null) {
            return;
        }

        if(root.left == null && root.right == null) {
            leafSize++;
        }

        getLeafNodeCount(root.left);
        getLeafNodeCount(root.right);
    }

    public int getLeafNodeCount2(TreeNode root) {
        if(root == null) {
            return 0;
        }
        if(root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.left) +
                getLeafNodeCount2(root.right);
    }
    //获取树的第k层有几个节点
    public int getKLevelNodeCount(TreeNode root,int k) {
        if(root == null) {
            return 0;
        }
        if(k == 1) {
            return 1;
        }
        return getKLevelNodeCount(root.left,k-1) +
                getKLevelNodeCount(root.right,k-1);
    }

    /**
     * 时间复杂度：O(N)
     * 空间复杂度：O(logN)
     * @param root
     * @return
     */
    public int getHeight(TreeNode root) {
        if(root == null) {
            return 0;
        }
        int leftHeight = getHeight(root.left);
        int rightHeight = getHeight(root.right);

        return Math.max(leftHeight,rightHeight)+1;
//        return leftHeight >rightHeight
//                ? leftHeight+1 : rightHeight+1;
    }

    /**
     * 时间复杂度：O(N)
     * 空间复杂度：O(logN)
     * @param root
     * @param val
     * @return
     */
    public TreeNode findVal(TreeNode root,char val) {
        if(root == null) {
            return null;
        }
        if(root.val == val) {
            return root;
        }
        TreeNode leftT = findVal(root.left,val);
        if(leftT != null) {
            return leftT;
        }
        TreeNode rightT = findVal(root.right,val);
        if(rightT != null) {
            return rightT;
        }
        return null;
    }
}
